Oddball Geological Features: Part 1 - The Chocolate Hills of Bohol

It occurred to me recently, that most of my posts are all work and hardly any play. The way I see it, I might as well do some leisurely writing from time to time that correlates with science (especially geology) to lighten the mood up a bit. With that being said, for the next week I’ll be writing about oddball geological features from around the world and solar system, that have interesting, questionable and sometimes legendary origins.

This amazing scenery is none other than the Chocolate Hills of Bohol, Philippines. Note the conical shape of the hills. [Image Source]

This week, I introduce to you the Chocolate Hills of the Bohol province in the Philippines! These peculiar, yet fascinating little grass covered hills are one the biggest tourist attractions out of all the islands in the country. They were given their name due to the brownish color the grass turns during the drier season (December till March) on the island. While the exact number is still unsure, as of right now the general consensus is that there are between 1,260 and 1,776 hills spread across the region. Their height can be anywhere from 30 to 50 meters (98 to 164 ft)– the highest one being 120 meters (130ft). In recognition of their scientific and geomorphic uniqueness, they were deemed the countries 3rd National Geological Monument on June 18th, 1988.

This diagram displays how karst formations occur. In the instance of the Chocolate Hills, the same process occurred, but over a very long period. [Image Source]

While the origin of the hills are somewhat disputed, it is generally accepted in the scientific community that they are a karst formation. More specifically, they are considered to be cockpit karst. What is karst? It is a topographical feature that forms when the dissolution of soluble rocks (e.g. limestone, gypsum, dolomite) takes place. Generally, karst landscapes have sinkholes, cliffs, underground streams, vast caverns and in the case of Bohol, hills. The Chocolate Hills are the result of tectonic processes that uplifted coral deposits from the ocean (largely limestone), which was then eroded away by means of tropical rainfall over millions of years.

Similar formations can be found in places such as Cuba, Jamaica, Indonesia, China, Malaysia and Puerto Rico, but the Chocolate Hills of Bohol are considered to be the crème de la crème of cockpit karst throughout the world. This is largely because of their aesthetically mesmerizing and conical nature. It should be noted, due to the landscape being predominately limestone, there are many caverns throughout the island of Bohol, which makes it a great destination for spelunking as well.

This image displays karst features in Guangxi Province of China. These hills formed in a very similar fashion as the Chocolate Hills of Bohol. [Image Source]

On a less scientific note, the natives of Bohol have some pretty awesome legends as to how the hills were created. Rather than telling all of the stories (let curiosity lead the way), I’m only going to mention the one I thought was the most intriguing:

As legend has it… Many years ago two feuding giants got into a bit of a quarrel on the island of Bohol. To resolve their differences, they began to hurl massive rocks, boulders and handfuls of sand at each other. This battle continued for days on end, until at one point, both giants became overly exhausted. In their state of exhaustion, it was by chance they had forgotten all about their “little” feud! As a result, they became homies, cracked open a couple beers and watched the sunset at the nearest beach; forgetting all about the mess they created from their feud, that is now known as the Chocolate Hills.

Okay, I may have given the story a bit of embellishment, but it seemed fitting. With that being said, I’d love to visit the Chocolate Hills one day. When I first saw the pictures of them, I couldn’t help but think how surreal they looked. The first thing that came to mind was, “That’s exactly what a tropical version of the Shire from The Lord of the Rings, would look like!” Whether it's just for an unforgettable view or some light spelunking, it would appear the Chocolate Hills are a bucket list worthy destination. With that being said, if you enjoyed reading this be sure to hit me up with a follow and check out my other recent posts on Subducting Seamounts and Accretion in the Marin Headlands of the San Francisco Bay. Also, if you would like to read more on geology and other interesting topics, check out @mountainwashere!

Bibliography:

https://en.wikipedia.org/wiki/Chocolate_Hills#Origin
https://en.wikipedia.org/wiki/Karst
http://whc.unesco.org/en/tentativelists/5024/
http://www.bohol-philippines.com/bohol-caves.html